1. Technical Field
The following description relates to one or more techniques, for an image forming apparatus, to generate a supply voltage depending on an operation mode and supplying the generated supply voltage to one or more loads.
2. Related Art
Various techniques have been proposed for reducing electric power consumption of a device configured to operate functional circuits, such as a driving circuit and a control circuit, in response to receipt of power supply from a power supply device. For example, a communication terminal device has been proposed, which is configured to reduce electric power consumption of the device as a whole by switching an operation mode between a normal operation mode and a power-saving mode (a low power consumption mode) depending on a usage state or an operating state of the device. It is noted that the normal operation mode is a mode where each functional circuit can operate in response to an electric power being supplied to the entire device from a main power supply. In addition, the power-saving mode is a mode where the electric power is supplied to one or more specific functional circuits from the main power supply.
However, according to the communication terminal device, since the main power supply performs the same operation (to generate a predetermined supply voltage) regardless of the operation mode, the power consumption of the main power supply hardly varies. Therefore, especially when the device is configured such that a variety of functional circuits thereof need respective operational supply voltages and the power-saving mode requires only the lowest operational supply voltage to be supplied (i.e., functional circuits which operate with higher operational supply voltages are deactivated in the power-saving mode), a problem is caused concerning wasteful power consumption in the main power supply.
A concrete example will be provided under the following assumption. The communication terminal device has a first load that operates with a first voltage and second and third loads that operate with a second voltage lower than the first voltage. The main power supply always generates and outputs the first voltage. To the first load, the first voltage is supplied as is from the main power supply. The second and third loads are supplied with the second voltage into which the first voltage from the main power supply has been converted via a regulator. In the power-saving mode, the third load is only supplied with the second voltage while the first and second loads are deactivated.
In the above example, the first load is not supplied with the first voltage in the power-saving mode. Further, the second load is not supplied with the second voltage from the regulator. Therefore, it is possible to save power consumption of the device as a whole. However, even in the power-saving mode, since the main power supply needs to output the first voltage, it is impossible to save power consumption of the main power supply.
In consideration of the above problem, a technique has been proposed to achieve power saving of the main power supply even in the power-saving mode. Specifically, a power supply circuit (corresponding to the aforementioned main power supply) generates the first voltage in the normal operation mode while the power supply circuit generates the second voltage in the power-saving mode. However, in this case, the regulator is as well supplied with the second voltage, and consequently cannot operate normally. Thus, the proposed technique is provided with an electric path through which an electric power is supplied from the power supply circuit to the third load without involving the regulator and a switch that selectively makes or breaks the electric path. Further, in this configuration, when the switch is turned on in the power-saving mode, the second voltage is supplied from the power supply circuit directly to the third load.
According to the proposed technique, in the power-saving mode, the power supply circuit generates the second voltage lower than the first voltage generated in the normal operation mode. Thus, it is possible to save the power consumption of the power supply circuit in the power-saving mode in comparison with the normal operation mode where the power supply circuit generates the first voltage.